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The role of regulatory T cells and anti-inflammatory cytokines in psoriasis.

Introduction

Psoriasis is a chronic inflammatory disease with a genetic predisposition that can be triggered by environmental factors. Pathogenesis is characterized by activation of the Th1/Th2 axis and abnormalities of the Th17/Treg balance (1). The current state of knowledge suggests that the Il-23/Thi7/Il-i7 axis plays a key role in the initiation of inflammatory psoriasis, known as "autoinflammation". The predominance of Thn/IFN-y and proinflammatory cytokines develops in the chronic phase (2-4). An essential factor of pathogenesis is the dysfunction of regulatory lymphocytes (Treg), which are involved in homeostasis mechanisms to maintain tolerance and prevent autoimmune disorders (5).

Treg cells are a subpopulation of lymphocytes responsible for suppressing an excessive or autoreactive immune response. They have the ability to interact directly through membrane receptors for immune cells (effector T-lymphocytes, memory and natural killer [NK] cells, B lymphocytes, antigen presenting cells) by creating suppressing cytokines (IL-10, IL-35, TGF-[beta], galectin-1) or by direct cytotoxic action (granzyme B and perforin release) (6-8). The important feature of Treg cells is a high expression of the IL-2 receptor chain (CD25), which is responsible for maintenance of tolerance to self-antigen because Treg cells bind IL-2 and decrease levels of IL-2, causing inhibition of T cells (9). Phenotypically, Treg cells express FOXP3, cytotoxic T lymphocyte-associated antigen-4 (CTLA4), certain members of toll-like receptors, CD103 ([alpha]E[beta]7integrin), glucocorticoid-induced TNF receptor family-related gene (GITR), lymphocyte activation gene-3, programmed death receptor-1, and neurophilin on their surface (9, 10). FOXP3 is a more specific marker of Treg cells than CD4 and CD25, and it is very important for the development and activity of Treg cells. Moreover, the expression of FOXP3 induces GITR, CD103, and CTLA-4 (11).

Some studies have shown that approximately 5% of Th cells in the blood express FOXP3, and about 20% of Th cells in the skin of adults. More than 95% of FOXP3-positive Th cells in the skin express CD45RO, but 75-80% are FOXP3-negative (12, 13).

Treg cells are a heterogeneous population consisting of cells with a variety of immunophenotypes: CD[4.sup.+]CD2[5.sup.+]FOXP[3.sup.+]T cells with characteristic expressions of the FOXP3 transcription factor with high CD25 expression and deficiency in expression of IL-7[alpha] subunit receptor (IL7R-[alpha] or CD127); CD8+CD25+FOXP3+ T lymphocytes, an analogous subpopulation to the previously mentioned one, are found among CD8+ T cells; Treg type 1 (Tri) are cells with the CD2[5.sup.-]FOXP[3.sup.-]CD[4.sup.+] phenotype that secrete significant amounts of interleukin 10 (IL-10) and transforming growth factor (TGF-[beta]); Th3 are phenotypically similar to Tr1 (CD2[5.sup.-]Foxp[3.sup.-]CD[4.sup.+]), but their main modulator is TGF-[beta]; and CD[8.sup.+]CD2[8.sup.-] lymphocytes do not express FOXP3 (7, 11, 14).

Treg cells consist of naturally developed cells (nTreg) in the thymus, and inducible Treg cells (iTreg), which transform into Treg cells in the periphery (11). Although iTreg resemble nTreg in phenotype and function, there are differences in epigenetic status and stability (12). Lymphocyte iTreg are Tr1 and Th3, which arise in the periphery from naive T cells under the antigen that is presented by immature dendritic cells with exposition of TGF-[beta] and IL-10 (11, 15). IL-10 is necessary to induce or suppress lymphocyte Tr1 and Th3, which depend on TGF-[beta]. Some Treg cells can induce the formation of other Treg cells under the influence of IL-35 (iTr35). IFN-y inhibits their activity (11, 15).

The best-known CD[4.sup.+]Tregs are FOXP[3.sup.+]Tregs and FOXP[3.sup.+]Tn. The mechanisms of FOXP[3.sup.+]Tregs and Tr1 action on adaptive immune responses is understandable, but is still ambiguous on innate immunity (16). Yao et al. observed that Tr1 can have a beneficial influence on disease-associated inflammasome activation by IL-10. Lymphocyte Tr1 inhibited the transcription of pro-IL-1b mRNA, inflammasome-mediated activation of caspase-1, and secretion of mature IL-1b (16).

Treg cells and psoriasis

The amount of Treg cells in psoriasis

Treg cells play a crucial role in psoriatic inflammation (5, 17). Interleukin-6, which is needed for the differentiation of Treg cells, inhibits the activation and proliferation of Th17, and leads to normalization of Treg cells and Th17 balance (1). Some researchers have found deviations in CD[4.sup.+]CD2[5.sup.+]FOXP[3.sup.+]Treg, and Furuhashi et al. (18) have noted the presence of CD[4.sup.-]FOXP[3.sup.+] in the peripheral blood of patients with psoriasis. Some authors have confirmed dysfunctional CD[4.sup.+]CD2[5.sup.+]FOXP[3.sup.+]Treg activity as a reason for hyperproliferation of T effectors in vivo. Karamehic et al. (5) have demonstrated a lower amount of CD[4.sup.+]CD2[5.sup.+]Treg in the blood of psoriatic patients compared to a control group, but there was no correlation with the severity of the disease (psoriasis areas severity index, PASI). Similarly, a Polish study by Pawlaczyk et al. (19) has shown a statistically significant decrease in Treg cells in flow cytometry in psoriasis patients with PASI > 12.

The literature shows many contradictory reports. Saito et al. (20) and Furuhashi et al. (18) did not find any difference in the percentage of Treg cells between psoriatic and healthy patients. Zhang et al. (21) even reported a greater amount of Treg cells in the blood of patients with acute psoriasis than in the control group.

FOXP[3.sup.+] cells were seldom present in healthy epidermis and dermis. Fujimura et al. (22) found more CD[3.sup.+], CD[4.sup.+], and CD2[5.sup.+]FOXP[3.sup.+]Treg in psoriatic epidermis than in the dermis. Leite Dantas et al. (23) described an inducible psoriasis-like arthritis by human TNF in transgenic mouse. The skin lesions were characterized by keratinocyte hyperproliferation, a high amount of proinflammatory cytokines with macrophages, and Th1 and Treg cell infiltration as in the psoriasis-like phenotype. Treg cells inhibit the pro-inflammatory activity of macrophages, which are the major immune effector cells in TNF-mediated psoriasis.

Keijsers et al. (24) examined biopsies from patients with chronic plaque psoriasis (n = 9): the center and margin of the lesion, and perilesional and non-lesional skin. They observed a significant increase of CD[3.sup.+], CD[4.sup.+], and FOXP[3.sup.+] cells from non-lesional skin compared to psoriatic skin. In seven of nine patients, the FOXP[3.sup.+]Treg/CD[4.sup.+] T cell ratio was higher in non-lesional skin than in perilesional and lesional skin, even in healthy skin. What is more, the expression of IL-17 was correlated with mast cells, but not with CD[4.sup.+] cells. The high FOXP3/CD4 ratio in the non-lesional skin of psoriatic patients showed active mechanisms of immune tolerance, whereas in perilesional and non-lesional skin the high activity of effector cells exacerbated the inflammation (24).

Differences in the amount of Treg cells may depend on the type of psoriasis. Yan et al. (25) have shown a greater number of FOXP[3.sup.+]Treg in plaque efflux compared to skin les ions in the guttate form. Another study showed a decrease in CD3[9.sup.+]FOXP3+, especially in the pustular and erythrodermic forms of psoriasis, and their number increased with the duration of the disease. It is questionable whether this can be connected with different pathogenic mechanisms for different types of psoriasis (26).

Dysfunction of Treg cells in psoriasis

The divergences of the studies cited above indicate that not the amount of Treg cells but their dysfunction may be significant in the pathogenesis of psoriasis. It has been found that Treg cells separated from the lesions or peripheral blood of psoriatic patients cannot properly suppress T effector responses due to alloantigenspecific or polyclonal TCR stimulation (12, 27). Sugiyama et al. (27) have observed their decreased cytotoxic activity, but only three patients were assessed. CD[4.sup.+]CD2[5.sup.+]Treg isolated from psoriatic lesions are not capable of suppressing effector activities of Th1 in the skin of people with psoriasis. In contrast, those isolated from non-psoriatic patients' peripheral blood are able to inhibit hyperactive psoriatic Th1 in vitro (6, 28-30). Thus, hyperproliferation of psoriatic pathogenic cells in vivo is a consequence of abnormal Treg cell activity in the blood and psoriatic lesions (12, 27).

Several studies have shown that Treg cells' function in psoriasis was inversely correlated with human CD127 expression (31-33). These disorders may be the result of abnormal CD127 expression in CD[4.sup.+]CD2[5.sup.+]lymphocytes (18). Zhao et al. (34) found strong expression of miR-210 (microRNAs: endogenous, noncoding RNAs) in CD[4.sup.+]cells, which inhibited expression of FOXP3, thereby causing Treg cell dysfunction and not reducing their numbers. In addition, it led to increased production of IFN-y and IL-17, and the decrease of IL-10 and TGF-[beta] in T CD[4.sup.+]. In contrast, Wang et al. (35) discovered the dysfunction of Treg cells by CD18 knockout (CD18hypo PL/J mice) as a causal factor of pathogenic T cell hyperproliferation in psoriasis. This reduced CD18 expression on CD[4.sup.+]CD2[5.sup.+]CD12[4.sup.-]Treg, compared to a wild type, which led to weak function and proliferation of Treg cells. The abnormal function of Treg cells can be reversed by transfer of CD18 Treg cells into mice with a CD18 defect, causing psoriasis improvement. Yang et al.

(36) revealed that psoriatic Treg cells show a predominant STAT3 phosphorylation pathway that leads to overproduction of proinflammatory cytokines (IL-6, IL-21, IL-23), resulting in T effector activation. In addition, Treg cells isolated from psoriatic patients could produce IFN-y, TNF-[alpha], and IL-17.

Th17 and Treg cells

Hyperactivation of TI117 is responsible for abnormalities of the Th17/Treg balance in psoriasis (1). Priyadarssini et al. (37) showed abnormalities in T cell phenotypes with an increase in Th1/Th17 and a relative decrease in Th2/Treg in psoriasis compared to healthy patients. They observed a linear trend of the Th1/Th17 percentage together with PASI increasing. These outcomes proved an immune-dysregulation in psoriasis, and connection between the Th1/Th17 phenotype and severity of the disease (37).

Lymphocyte Th17 development is functionally linked to the development of FOXP[3.sup.+]Treg and they share the requirement for TGF-[beta] to develop from naive T cells. When activated in the presence of TGF-[beta] or TGF-[[beta].sup.+]IL-6, naive T cells start to simultaneously upregulate both FOXP3 and RORyt, and it has been shown that these transcription factors can directly interact with each other (38, 39). Thus, the competition of Treg cells with Th17 for their reciprocal development from this common precursor can already be seen as a way to control Th17 or Treg cell development, respectively (38, 39). In patients with psoriasis, the impaired function of Treg cells causes the hyperactivation of Th1 and TI117, which causes psoriatic inflammation (5, 40, 41). Zhang et al. (21) revealed an increasing amount of TI117 and FOXP[3.sup.+]Treg in the blood and lesions in psoriatic patients and a positive correlation with severity of the disease. The correlation of Th17/Treg ratio in skin lesions with PASI was inverse, but in blood it was positive.

However, Bovenshen et al. (28) discovered that FOXP[3.sup.+]Treg isolated from psoriatic lesions can easily differentiate into a strong proinflammatory IL-17A-positive TI117, which expresses three cell surface markers, IL-17[A.sup.+], FOXP[3.sup.+], and CD[3.sup.+]. They might significantly contribute to the disease development. These cells produce IL-17A and IL-22, and show RORyt expression. In severe psoriasis, the expression of RORyt is increased, and FOXP3 of the Treg marker decreases, which may suggest that Treg cells take part in perpetuating the inflammatory process rather than in suppressing it (28, 42).

Treg cells and psoriasis therapy

Treg cells are up-regulated by drug therapy in psoriasis. The longterm remission is connected with normalization of the Treg cells and pathogenic memory/effector cell balance (10). After an effective monoclonal antibody therapy (infliximab, etanercept, and efalizumab), an increase of CD[4.sup.+]CD[25.sup.+]FOXP[3.sup.+] cells in the blood of psoriatic patients is observed as well as in the previously affected skin after treatment with adalimumab (17, 24, 43). Quaglino et al. (43) noted Th1/Th17 hyperactivity with Treg cell down-regulation at baseline, and after etanercept treatment the normalization of their activity. Therefore, stimulating Treg cell activity can be dependent on the anti-TNF mechanism (17). Alefacept inhibits T effectors by apoptosis of T cells (releasing granzymes by the NK cells). The apoptosis is enhanced by Treg cells and causes remission of the disease in responding patients (10). Furuhashi et al. (18) evaluated the amount of Treg cells in blood before treatment and after photochemotherapy treatment. For patients that achieved PASI 90, the amount of Treg cells was significantly higher than for those that did not have PASI 90. Moreover, UVB can induce Treg cell production (10). Similarly, Kubo et al. (44) proved that bath-PUVA (psoralen and UVA) therapy significantly increases the number of Treg cells and restores Treg cell function to almost normal in most patients with psoriasis. Variations of Treg cell amounts during various therapies may explain why some of them (methotrexate and cyclosporine) resulted in very short remissions, and others (alefacept and UVB) in long-term ones (10). Therefore, one should ask whether, after determining Treg cells, it is possible to predict a good response to the treatment (17, 18).

Mattozzi et al. (41) also described the relationship between vitamin D and Treg cells in psoriasis. They assessed whether vitamin D status is correlated with circulating Treg cells and PASI. In contrast, low titer encourages the activity of Tin, TI117, and Th22. The immune modulator properties of vitamin D are mediated in part through its effects on Treg cells.

Interesting research findings were shown by Ma et al. (45). They analyzed patients during anti-TNF treatment with manifestation of psoriasis-like disease. They noticed that the neutralization of TNF-[alpha] did not cause the production of proinflammatory cytokines (IL-1[beta], IL-6, IL-17, IL-21, and IL-22), but it suppressed FOXP3 expression in the skin with reduction of FOXP3 (+)Treg (45) (Table 1).

Interleukin-10 and psoriasis

IL-10 has an anti-inflammatory effect, inhibiting the production of pro-inflammatory cytokines such as IFN-y, IL-2, IL-3, TNF-[alpha], or GMCSF. It is produced by Treg lymphocytes, but also by macrophages, dendritic cells, and B lymphocytes (46, 47). Interleukin-10 inhibits the production of IL-12 by macrophages, and IL-12 stimulates IFN-y secretion. Therefore, IL-10 is considered the most important inhibitor of INF-y activity (46). Moreover, IL-10 inhibits Th1 and promotes Th2 responses, and inhibits TI117 responses in mice (46, 48). It also has the ability to inhibit the expression of co-stimulating molecules and MHC II on dendritic cells and macrophages. In addition, it also blocks NF-KB activity and is involved in regulating the JAK-STAT signaling pathway (49). IL-10 can inhibit cyclooxygenase-2 (COX-2). Its deficiency causes COX-2 activation and increased production of thromboxane A2, causing vascular and cardiovascular endothelial dysfunction in mice. Mice with congenital deficiency of IL-10 develop atherosclerotic abnormalities in vessels much faster (49). In psoriatic fibroblast studies that were stimulated with IL-8 and TNF, Glowacka et al. (50) showed that they are not able to produce IL-10, but neutrophils released IL-10 in a very low concentration.

Relative IL-10 deficiency in serum and skin in patients with psoriasis is an essential factor in pathogenesis (51). The beneficial effects of recombinant human IL-10 treatment have been suggested for psoriasis treatment (46, 51, 52). Clinical trials in psoriatic patients showed improvement in the reduction in relapse rate and good tolerance. Anti-psoriatic action of interleukin-10 inhibits antigen-presenting cells (inhibition of MHC II expression and coagulating molecules) and shifts the ratio between Th1 and Th2 cells, rather than by acting directly on keratinocytes. It promotes the production of cytokines by Th2 through inhibition of IFN-y and it inhibits Th1 activity through suppression of IL-12 synthesis (51). This causes a decrease in the chemotactic concentration of IL-8 neutrophils in the efflorescence, limiting the formation of microtubules (51, 53). Docke et al. (46) reported the effect of systemic IL-10 in 7-week therapy in 10 psoriasis patients. In addition to clinical improvement, they also observed the activation of NK cells and an increase in proinflammatory indicators (CRP and soluble IL-2R). Some medications, such as apremilast, a phosphodiesterase inhibitor, can inhibit intracellular cAMP, increasing the amount of IL-10 (54).

Recently, a specific subset of IL-10-producing regulatory B cells was identified as so-called Bregs, which are major negative regulators of the immune response (55, 56). They inhibit differentiation of Th1 and TI117 (57, 58). Psoriasis is characterized by a significant decrease in their amount, although the number of progenitor B cells is even increased, suggesting that Bregs may be functionally impaired in psoriasis (55, 59). Mavropulos et al. (57) proved that there is a decrease in IL-[10.sup.+]B cells and an inverse correlation with PASI, IL-17[A.sup.+]CD[3.sup.+], and IFN[y.sup.+]CD[3.sup.+] T cells.

Recently many studies have been concerned with IL-10 gene polymorphisms in psoriasis, especially the promoter region (60). Studies by Asadullah et al. (61) have shown that IL-10.G13 allele polymorphism is associated with familial predisposition to psoriasis. Asian meta-analysis showed a strong association between psoriasis and the IL-10-1082G allele (62).

Interleukin-10 is an important modulator of HLA-G expression in the CD1[4.sup.+] monocytes in blood. HLA-G is a molecule with immunosuppressive properties. Its deficiency in membrane-bound and soluble form can cause abnormalities in immune responses that lead to autoimmune diseases (63, 64).

Aractingi et al. (65) revealed the presence of HLA-G protein in psoriatic lesions, but never in normal healthy skin, such that it can be an inhibitor for T cells. They described lower plasma levels of sHLA-G and IL-10 in psoriatic patients compared to healthy volunteers (63). Borghi et al. (63) showed that treatment of psoriasis leads to suppression of Th1 activation because of sHLA-G secretion by an IL-10.

Transforming growth factor [beta] and psoriasis

TGF-[beta] is an important regulator in maintaining immune homeostasis. Disorders in TGF-[beta]-expression or TGF-[beta]-response play an important role in autoimmune diseases, chronic inflammatory conditions, parasitic infections, neurodegenerative diseases, cancer, and chronic rejections of transplants (66). General administration of TGF-[beta] suppresses the symptoms of autoimmune diseases, whereas anti-TGF-[beta] antibodies cause disease progression (67). Mutations within the TGF-[beta] gene result in a phenotype characteristic for autoimmune diseases (67). TGF-[beta] inhibits macrophage activity, although it can be produced by them. It also inhibits the activity of neutrophils, stimulates fibroblast proliferation and production of extracellular matrix elements by these cells, and activates angio-genesis (68).

TGF-[beta] also has the ability to regulate the T lymphocyte subpopulation. It promotes the development of the Th17 response by using peripheral FOXP[3.sup.+]Treg while inhibiting the development of

Thi and Th2 lines (69). In addition, TT13 is produced under high concentrations in the TGF-[beta] microalgae, and when fully mature they secrete large amounts of TGF-[beta], modulating immunoreactivity (70). TGF-[beta] suppressive effects on T lymphocytes, B lymphocytes, and macrophages, and the effect on T cell effector memory transformation have been demonstrated. Moreover, it cooperates with CTLA-4 to suppress the immune response, and also inhibits the expression of adhesion molecules and thus the adhesion of leukocytes to endothelial cells (70, 71).

The role of TGF-[beta] in psoriasis is still not fully explained. A significant decrease in its receptors in the epidermis has been observed (72, 73). TGF-[beta]i is a potent growth inhibitor for keratinocytes, and limiting its signaling increases keratinocyte hyperproliferation in psoriasis. Flisiak et al. (74) reported higher TGF-[beta]i expression in the epidermis and serum in psoriatic patients, and TGF-[beta]i correlation with PASI (74, 75). In addition, effective treatment resulted in TGF-[beta]i serum reduction (76). Moreover, abnormal signaling of TGF-[beta] discovered in psoriasis, even in the presence of higher TGF-[beta] expression, stimulates hyperproliferation of psoriatic keratinocytes (77). The mechanism responsible for increasing TGF-[beta] levels in psoriatic patients' serum may be due to stromal cells (74). Based on clinical data, it is difficult to evaluate whether increased TGF-[beta]1 is a reason for psoriatic inflammation, or is a result.

In a study by Zaher et al. (78), TGF-[beta]i concentration was slightly higher in the healthy skin of the control group compared to the non-lesional skin of psoriatic patients. In contrast, Li et al. (79) suggest that even physiological doses of TGF-[beta]i may contribute to the development of psoriasis. Contrary to plasma concentrations, TGF-[beta]i levels in psoriasis are still contradictory. TGF-[beta]1 regulation in psoriatic plaques requires further analysis.

TGF-[beta]i is a potent inhibitor of keratinocyte growth and, on the other hand, one can observe its overexpression in psoriatic keratinocytes. The fact that it seemed to react with different growth factors concomitantly with inflammation requires further explanation. Transgenic mice expressing wild-type TGF-[beta]i in the epidermis develop skin lesions in the form of psoriasis efflux (68). These lesions are characterized by hyperproliferation of the epidermis, massive infiltration of neutrophils, T lymphocytes, and macrophages to the epidermis and superficial dermis, basophilic degradation, and angiogenesis as in Thi-mediated inflammatory skin diseases such as psoriasis (79). After biologic treatment (etanercept and efalizumab), TGF-[beta]i levels have been decreased together with PASI in mild psoriasis (68).

Recent research by Litvinov et al. (77) has identified CD109 as a new co-receptor and negative regulator of TGF-[beta] signaling. A decreased expression of TGF-[beta] receptors is observed compared to CDi09 release in keratinocytes in vitro in psoriatic epidermis (77).

Another crucial part of the analysis of the role of TGF in psoriasis is assessing its isoforms (TGF-[beta]i, TGF-[beta]2, and TGF-[beta]3), which bind specific receptors (TGF[beta]RI, TGF[beta]RII, and TGF[beta]RIII). Activation of receptors turns on the SMAD intracellular signaling pathway (80). A study by Yu et al. (81) showed lower expression of TGF[beta]RI and SMAD2, SMAD4, and SMAD6 mRNA in lesions and non-lesional skin in psoriasis. SMAD7 mRNA expression was remarkably lower in lesions compared with non-lesional and healthy skin. TGF-[beta]3 and TGF[beta]RII mRNA were found only in non-lesional skin without differences in TGF-[beta]i and TGF-[beta]2 expression. Processes of TGF-[beta] isoform regulation in psoriatic plaques need more analyses.

Recent studies by Szondy et al. (82) have shown that treatment with anti-TNF-[alpha] is not only related to neutralization of the effects of this molecule, but also leads to TGF-[beta] production in macrophages (82).

Conclusion

In the literature, there have been conflicting reports on the role of different types of regulatory cells and anti-inflammatory cytokines in psoriasis and immune tolerance mechanisms. Full understanding of these processes can develop new therapies for this disease.

References

(1.) Deng Y, Chang C, Lu Q. The inflammatory response in psoriasis: a comprehensive review. Clin Rev Allergy Immunol. 2016;50:377-89.

(2.) Christophers E, Metzler G, Rocken M. Bimodal immune activation in psoriasis. Br J Dermatol. 2014;170:59-65.

(3.) Martin DA, Towne JE, Kricorian G, Klekotka P, Gudjonsson JE, Krueger JE, et al. The emerging role of IL-17 in the pathogenesis of psoriasis: preclinical and clinical findings. J Invest Dermatol. 2013;133:17-26.

(4.) Owczarczyk-Saczonek A, Placek W. tuszczyca jako choroba autoimmunologiczna. [Psoriasis as an autoimmune disease]. Przeglad Dermatologiczny. 2014;101:278-87. Polish.

(5.) Karamehic J, Zecevic L, Resic H, Jukic M, Jukic T, Ridjic O, et al. Immunophenotype lymphocyte of peripheral blood in patients with psoriasis. Med Arch. 2014;68:236-8.

(6.) Birch KE, Vukmanovic-Stejic M, Reed JR, Akbar AN, Rustin MHA. The immunomodulatory effects of regulatory T cells: implications for immune regulation in the skin. Br J Dermatol. 2005;152:409-17.

(7.) Kondelkova K, Vokurkova D, Krejsek J, Borska L, Fiala Z, Hamakova K, et al. The number of immunoregulatory T cells is increased in patients with psoriasis after Goeckerman therapy. Acta Medica (Hradec Kralove). 2012;22:91-5.

(8.) Vignali DA, Collison LW, Workman CJ. How regulatory T cells work. Nat Rev Immunol. 2008;8:523-32.

(9.) Liu H, Leung BP. CD4+CD25+ regulatory T cells in health and disease. Clin Exp Pharmacol Physiol. 2006;33:519-24.

(10.) Kagen MH, McCormick TS, Cooper KD. Regulatory T cells in psoriasis. Ernst Schering Res Found Workshop. 2006;56:193-209.

(11.) Broere F, Apasov SG, Sitkovsky MV, van Eden W. A2 T cell subsets and T cellmediated immunity. In: Nijkamp F, Parnham M., editors. Principles of Immunopharmacology. Basel: Birkhauser; 2011. p. 15-27.

(12.) Karczewski J, Dobrowolska A, Rychlewska-Hanczewska A, Adamski Z. New insights into the role of T cells in pathogenesis of psoriasis and psoriatic arthritis. Autoimmunity. 2016;49:435-50.

(13.) Sanchez Rodriguez R, Pauli ML, Neuhaus IM, Yu SS, Arron ST, Harris HW, et al. Memory regulatory T cells reside in human skin. J Clin Invest. 2014;124:1027-36.

(14.) Gol-Ara M, Jadidi-Niaragh F, Sadria R, Azizi G, Mirshafiey A. The role of different subsets of regulatory T cells in immunopathogenesis of rheumatoid arthritis. Arthritis. 2012;2012:e805875.

(15.) Zeng H, Zhang R, Jin B, Chen L. Type 1 regulatory T cells: a new mechanism of peripheral immune tolerance. Cell Mol Immunol. 2015;12:566-71.

(16.) Yao Y, Vent-Schmidt J, McGeough MD, Wong M, Hoffman HM, Steiner TS, et al. Tr1 cells, but not Foxp3+ Regulatory T cells, suppress NLRP3 inflammasome activation via an IL-10-dependent mechanism. J Immunol. 2015;195:488-97.

(17.) Richetta AG, Mattozzi C, Salvi M, Giancristoforo S, D'epiro S, Milana B, et al. CD4+ CD25+ T-regulatory cells in psoriasis. Correlation between their numbers and biologics--induced clinical improvement. Eur J Dermatol. 2011;21:344-8.

(18.) Furuhashi T, Saito C, Torii K, Nishida E, Yamazaki S, Morita A. Photo(chemo) therapy reduces circulating Th17 cells and restores circulating regulatory T cells in psoriasis. PLoS One. 2013;8:e54895.

(19.) Pawlaczyk M, Karczewski J, Wiktorowicz K. T regulatory CD4+CD25high lymphocytes in peripheral blood of patients suffering from psoriasis. Adv Dermatol Alergol. 2010;27:25-8.

(20.) Saito C, Maeda A, Morita A. Bath-PUVA therapy induces circulating regulatory T cells in patients with psoriasis. J Dermatol Sci. 2009;53:231-3.

(21.) Zhang J, Lin Y, Li C, Zhang X, Cheng L, Dai L, et al. IL-35 decelerates the inflammatory process by regulating inflammatory cytokine secretion and M1/M2 macrophage ratio in psoriasis. J Immunol. 2016;197:2131-44.

(22.) Fujimura T, Okuyama R, Ito Y, Aiba S. Profiles of Foxp3+ regulatory T cells in and mycosis fungoides. Br J Dermatol. 2008;158:1256-63.

(23.) Leite Dantas R, Masemann D, Schied T, Bergmeier V, Vogl T, Loser K, et al. Macrophage-mediated psoriasis can be suppressed by regulatory T lymphocytes. J Pathol. 2016;240:366-77.

(24.) Keijsers RR, van der Velden HM, van Erp PE, de Boer-van Huizen RT, Joosten I, Koenen HJ, et al. Balance of Treg vs. T-helper cells in the transition from symptomless to lesional psoriatic skin. Br J Dermatol. 2013;168:1294-302.

(25.) Yan KX, Fang X, Han L. Foxp3+ regulatory T cells and related cytokines differentially expressed in plaque vs. guttate psoriasis vulgaris. Br J Dermatol. 2010;163:48-56.

(26.) Zhang HY, Yan KX, Huang Q, Ma Y, Fang X, Han L. Target tissue ectoenzyme CD39/CD73-expressing Foxp3+ regulatory T cells in patients with psoriasis. Clin Exp Dermatol. 2015;40:182-91.

(27.) Sugiyama H, Gyulai R, Toichi E, Garaczi E, Shimada S, Stevens SR, et al. Dysfunctional blood and target tissue CD4+CD25 high regulatory T cells in psoriasis: mechanism underlying unrestrained pathogenic effector T cell proliferation. J Immunol. 2005;174:164-73.

(28.) Bovenschen HJ, van de Kerkhof PC, van Erp PE, Woestenenk R, Joosten I, Koenen HJ. Foxp3+ regulatory T cells of psoriasis patients easily differentiate into IL-17Aproducing cells and are found in lesional skin. J Invest Dermatol. 2011;131:1853-60.

(29.) Bovenschen HJ, van Vlijmen-Willems IM, van de Kerkhof PC, van Erp PE. Identification of lesional CD4+ CD25+ Foxp3+ regulatory T cells in psoriasis. Dermatology. 2006;213:111-7.

(30.) Kagen MH, McCormick TS, Cooper KD. Regulatory T cells in psoriasis. Ernst Schering Res Found Workshop. 2006;56:193-209.

(31.) Banham AH. Cell-surface IL-7 receptor expression facilitates the purification of FOXP3(+) regulatory T cells. Trends Immunol. 2006;27:541-4.

(32.) Liu W, Putnam AL, Xu-Yu Z, Szot GL, Lee MR, Zhu S, et al. CD127 expression inversely correlates with FoxP3 and suppressive function of human CD4+ T reg cells. J Exp Med. 2006;203:1701-11.

(33.) Smolders J, Thewissen M, Peelen E, Menheere P, Tervaert JW, Damoiseaux J, et al. Vitamin D status is positively correlated with regulatory T cell function in patients with multiple sclerosis. PLoS One. 2009;4:e6635.

(34.) Zhao M, Wang LT, Liang GP, Zhang P, Deng XJ, Tang Q, et al. Up-regulation of microRNA-210 induces immune dysfunction via targeting FOXP3 in CD4(+) T cells of psoriasis vulgaris. Clin Immunol. 2014;150:22-30.

(35.) Wang H, Peters T, Sindrilaru A, Kess D, Oreshkova T, Yu XZ, et al. TGF-[beta]-dependent suppressive function of Tregs requires wild-type levels of CD18 in a mouse model of psoriasis. J Clin Invest. 2008;118:2629-39.

(36.) Yang L, Li B, Dang E, Jin L, Fan X, Wang G. Impaired function of regulatory T cells in patients with psoriasis is mediated by phosphorylation of STAT3. J Dermatol Sci. 2016;81:85-92.

(37.) Priyadarssini M, Divya Priya D, Indhumathi S, Rajappa M, Chandrashekar L, Thappa DM. Immunophenotyping of T cells in the peripheral circulation in psoriasis. Br J Biomed Sci. 2016;73:174-9.

(38.) Lochner M, Wang Z, Sparwasser T. The special relationship in the development and function of T helper 17 and regulatory T cells. Prog Mol Biol Transl Sci. 2015;136:99-129.

(39.) Zhou L, Lopes JE, Chong MM, Ivanov II, Min R, Victora GD, et al. TGF-beta-induced Foxp3 inhibits T(H)17 cell differentiation by antagonizing RORgammat function. Nature. 2008;453:236-40.

(40.) Lowes MA, Kikuchi T, Fuentes-Duculan J, Cardinale I, Zaba LC, Haider AS, et al. Psoriasis vulgaris lesions contain discrete populations of Th1 and Th17 T cells. J Invest Dermatol. 2008;128:1207-11.

(41.) Mattozzi C, Paolino G, Salvi M, Macaluso L, Luci C, Morrone S, et al. Peripheral blood regulatory T cell measurements correlate with serum vitamin D level in patients with psoriasis. Eur Rev Med Pharmacol Sci. 2016;20:1675-9.

(42.) Soler DC, McCormick TS. The dark side of regulatory T cells in psoriasis. J Invest Dermatol. 2011;131:1785-6.

(43.) Quaglino P, Bergallo M, Ponti R, Barberio E, Cicchelli S, Buffa E, et al. Th1, Th2, Th17 and regulatory T cell pattern in psoriatic patients: modulation of cytokines and gene targets induced by etanercept treatment and correlation with clinical response. Dermatology. 2011;223:57-67.

(44.) Kubo R, Muramatsu S, Sagawa Y, Saito C, Kasuya S, Nishioka A, et al. Bath-PUVA therapy improves impaired resting regulatory T cells and increases activated regulatory T cells in psoriasis. J Dermatol Sci. 2017;86:46-53.

(45.) Ma HL, Napierata L, Stedman N, Benoit S, Collins M, Nickerson-Nutter C, et al. Tumor necrosis factor alpha blockade exacerbates murine psoriasis-like disease by enhancing Th17 function and decreasing expansion of Treg cells. Arthritis Rheum. 2010;62:430-40.

(46.) Docke WD, Asadullah K, Belbe G, Ebeling M, Hoflich C, Friedrich M, et al. Comprehensive biomarker monitoring in cytokine therapy: heterogeneous, timedependent, and persisting immune effects of interleukin-10 application in psoriasis. J Leukoc Biol. 2009;85:582-93.

(47.) Tedgui A, Mallat Z. Interleukin-10: an anti-atherogenic cytokine. Pathol Biol (Paris). 2001;49:107-8.

(48.) Gu Y, Yang J, Ouyang X, Liu W, Li H, Yang J, et al. Interleukin 10 suppresses Th17 cytokines secreted by macrophages and T cells. Eur J Immunol. 200838:1807-

(49.) Sikka G, Miller KL, Steppan J, Pandey D, Jung SM, Fraser CD 3rd, et al. Interleukin 10 knockout frail mice develop cardiac and vascular dysfunction with increased age. Exp Gerontol. 2013;48:128-35.

(50.) Glowacka E, Lewkowicz P, Rotsztejn H, Zalewska A. IL-8, IL-12 and IL-10 cytokines generation by neutrophils, fibroblasts and neutrophils- fibroblasts interaction in psoriasis. Adv Med Sci. 2010;55:254-60.

(51.) Asadullah K, Sabat R, Friedrich M, Volk HD, Sterry W. Interleukin-10: an important immunoregulatory cytokine with major impact on psoriasis. Curr Drug Targets Inflamm Allergy. 2004;3:185-92.

(52.) Kimball AB, Kawamura T, Tejura K, Boss C, Hancox AR, Vogel JC, et al. Clinical and immunologic assessment of patients with psoriasis in a randomized, doubleblind, placebo-controlled trial using recombinant human interleukin 10. Arch Dermatol. 2002;138:1341-6.

(53.) Al-Robaee AA, Al-Zolibani AA, Al-Shobili HA, Kazamel A, Settin A. IL-10 implications in psoriasis. Int J Health Sci. 2008;2:53-8.

(54.) Schafer P. Apremilast mechanism of action and application to psoriasis and psoriatic arthritis. Biochem Pharmacol. 2012;83:1583-90.

(55.) Traupe H. Psoriasis and the interleukin-10 family: evidence for a protective genetic effect, but not an easy target as a drug. Br J Dermatol. 2017;176:1438-9.

(56.) Yanaba K, Kamata M, Ishiura N, Shibata S, Asano Y, Tada Y, et al. Regulatory B cells suppress imiquimod-induced, psoriasis-like skin inflammation. J Leukoc Biol. 2013;94:563-73.

(57.) Mavropoulos A, Varna A, Zafiriou E, Liaskos C, Alexiou I, Roussaki-Schulze A, et al. IL-10 producing Bregs are impaired in psoriatic arthritis and psoriasis and inversely correlate with IL-17- and IFN[gamma]-producing T cells. Clin Immunol. 2017;184:33-41.

(58.) Flores-Borja F, Bosma A, Ng D, Reddy V, Ehrenstein MR, Isenberg DA, et al. CD19+CD24hiCD38hi B cells maintain regulatory T cells while limiting TH1 and TH17 differentiation. Sci Transl Med. 2013;5:173ra23.

(59.) Hayashi M, Yanaba K, Umezawa Y, Yoshihara Y, Kikuchi S, Ishiuji Y, et al. IL10-producing regulatory B cells are decreased in patients with psoriasis. J Dermatol Sci. 2016;81:93-100.

(60.) Trifunovic J, Miller L, Debeljak Z, Horvat V. Pathologic patterns of interleukin 10 expression--a review. Biochem Med (Zagreb). 2015;25:36-48.

(61.) Asadullah K, Sterry W, Volk HD. Interleukin-10 and Psoriasis: Madame Curie Bioscience Database [Internet]: Austin (TX), Landes Bioscience. 2000-2013.

(62.) Lee YH, Choi SJ, Ji JD, Song GG. Associations between interleukin-10 polymorphisms and susceptibility to psoriasis: a meta-analysis. Inflamm Res. 2012;61:657-63.

(63.) Borghi A, Fogli E, Stignani M, Melchiorri L, Altieri E, Baricordi O, et al. Soluble human leukocyte antigen-G and interleukin-10 levels in plasma of psoriatic patients: preliminary study on a possible correlation between generalized immune status, treatments and disease. Arch Dermatol Res. 2008;300:551-9.

(64.) Moreau P, Adrian-Cabestre F, Menier C, Guiard V, Gourand L, Dausset J, et al. IL10 selectively induces HLA-G expression in human trophoblast and monocytes. Int Immunol. 1999;11:803-11.

(65.) Aractingi S, Briand N, Le Danff C, Viguier M, Bachelez H, Michel L, et al. HLA-G and NK receptors are expressed in psoriatic skin: a possible pathway for regulating infiltrating T cells? Am J Pathol. 2001;159:71-7.

(66.) Hahm KB, Im YH, Lee C, Parks WT, Bang YJ, Green JE, et al. Loss of TGF-[beta] signaling contributes to autoimmune pancreatitis. J Clin Invest. 2000;105:1057-65.

(67.) Krzemien S, Knapczyk P. Aktualne poglady dotycza.ce znaczenia transformujacego czynnika wzrostu beta (TGF-[beta]) w patogenezie niektorych stanow chorobowych. Wiad Lek. 2005;58:536-9. Polish.

(68.) Kallimanis PG, Xenos K, Markantonis SL, Stavropoulos P, Margaroni G, Katsambas A, et al. Serum levels of transforming growth factor-beta1 in patients with mild psoriasis vulgaris and effect of treatment with biological drugs. Clin Exp Dermatol. 2009;34:582-6.

(69.) Zhu J, Yamane H, Paul WE. Differentiation of effector CD4 T cell populations. Ann Rev Immunol. 2010;28:445-89.

(70.) Wan YY, Flavell RA. "Yin-yang" functions of TGF-[beta] and Tregs in immune regulation. Immunol Rev. 2007;220:199-213.

(71.) Prud'homme GJ, Piccirillo CA. The inhibitory effects of transforming growth factor-beta-1 (TGF-beta1) in autoimmune diseases. J Autoimmun. 2000;14:23-42.

(72.) Doi H, Shibata MA, Kiyokane K, Otsuki Y. Downregulation of TGFbeta isoforms and their receptors contributes to keratinocyte hyperproliferation in psoriasis vulgaris. J Dermatol Sci. 2003;33:7-16.

(73.) Han G, Williams CA, Salter K, Garl PJ, Li AG, Wang XJ. A role for TGFbeta signaling in the pathogenesis of psoriasis. J Invest Dermatol. 2010;130:371-7.

(74.) Flisiak I, Zaniewski P, Chodynicka B. Plasma TGF-beta1, TIMP-1, MMP-1 and IL-18 as a combined biomarker of psoriasis activity. Biomarkers. 2008;13:549-56.

(75.) Flisiak I, Chodynicka B, Porebski P, Flisiak R. Association between psoriasis severity and transforming growth factor beta (1) and beta (2) in plasma and scales from psoriatic lesions. Cytokine. 2002;19:121-5.

(76.) Flisiak I, Porebski P, Flisiak R, Chodynicka B. Plasma transforming growth factor beta1 as a biomarker of psoriasis activity and treatment efficacy. Biomarkers. (2003) ;8:437-43.

(77.) Litvinov IV, Bizet AA, Binamer Y, Jones DA, Sasseville D, Philip A. CD109 release from the cell surface in human keratinocytes regulates TGF-[beta] receptor expression, TGF-[beta] signalling and STAT3 activation: relevance to psoriasis. Exp Dermatol. 2011;20:627-32.

(78.) Zaher H, Shaker OG, EL-Komy MH, El-Tawdi A, Fawzi M, Kadry D. Serum and tissue expression of transforming growth factor beta 1 in psoriasis. J Eur Acad Dermatol Venereol. 2009;23:406-9.

(79.) Li AG, Wang D, Feng XH, Wang XJ. Latent TGFbetai overexpression in keratinocytes results in a severe psoriasis-like skin disorder. EMBO J. 2004;23:1770-81.

(80.) Derynck R, Zhang YE. Smad-dependent and Smad-independent pathways in TGF-beta family signaling. Nature. 2003;425:577-84.

(81.) Yu H, Mrowietz U, Seifert O. Downregulation of SMAD2, 4 and 6 mRNA and TGFbeta receptor I mRNA in lesional and non-lesional psoriatic skin. Acta Derm Venereol. 2009;89:351-6.

(82.) Szondy Z, Pallai A. Transmembrane TNF-alpha reverse signaling leading to TGFbeta production is selectively activated by TNF targeting molecules: Therapeutic implications. Pharmacol Res. 2017;115:124-32.

Agnieszka Owczarczyk-Saczonek (1), Joanna Czerwinska (1), Waldemar Placek (1)

(1) Department of Dermatology, Sexually Transmitted Diseases, and Clinical Immunology, University of Warmia and Mazury, Olsztyn, Poland. Corresponding author: aganek@wp.pl

Received: 23 August 2017 | Returned for modification: 19 November 2017 | Accepted: 1 December 2017

doi: 10.15570/actaapa.2018.4
Table 1 | Psoriasis and Treg disorders.

Category / Study            Examined       Finding

Amount of Treg
cells in blood
Karamehic et al. (5)        CD4+CD25+Treg  Decrease in peripheral
                                           blood, no correlation
                                           with PASI
Pawlaczyk et al. (19)       iTreg          Decrease in peripheral
                                           blood, correlation with PASI
                                           > 12
Saito et al. (20)           Treg           No differences between
                                           psoriatic and healthy
                                           patients
Furuhashi et al. (18)       Treg           No differences between
                                           psoriatic and healthy
                                           patients
Zhang et al. (21)           TTreg          Greater amounts
                                           in peripheral blood of
                                           patients with acute psoriasis
                                           than in the control group
Amount of Treg cells
in psoriatic lesion
Fujimura et al. (22)        CD[3.sup.+],   More in psoriatic
                            CD[4.sup.+],   epidermis than in dermis
                            CD2[5.sup.+]
                            FOXP[3.sup.+]
                            Treg
Keijsers et al. (24)        CD[3.sup.+],   Significant increase in
                            CD[4.sup.+],   non-lesional skin compared
                                           to psoriatic lesions
                            CD2[5.sup.+]
                            FOXP[3.sup.+]
                            Treg
Yan et al. (25)             FOXP[3.sup.+]  Greater number in chronic
                            Treg           plaques compared to skin
                                           lesions in the guttate form
Zhang et al. (26)           CD3[9.sup.+]   Decrease in the pustular
                            FOXP[3.sup.+]  and erythrodermic psoriatic
                                           lesions
Dysfunction of Treg cells
Sugiyama et al. (27)        CD[4.sup.+]    Decreased cytotoxic activity
                            CD2[5.sup.+]   of Treg cells from psoriatic
                            Treg           lesions
                                           Not capable of suppressing
                                           Th1 in psoriatic lesions
                                           Isolated from non-psoriatic
                                           patients' peripheral blood,
                                           able to inhibit hyperactive
                                           psoriatic Th1 in vitro
Sugiyama et al. (27)        Treg           Hyperproliferation of
                                           psoriatic pathogenic cells
                                           in vivo is a consequence of
                                           abnormal
Zhang et al. (26)                          Treg cell activity in blood
                                           and psoriatic lesions
Bovenschen
HJ et al. (28)
Zhao et al. (34)            CD[4.sup.+]    Strong expression of miR-210,
                            CD2[5.sup.+]   which inhibited expression of
                            Treg           FOXP3, thereby causing
                                           Treg cell dysfunction, not
                                           reducing their numbers and
                                           leading to increased
                                           production of IFN-y, IL-17,
                                           and the decrease of IL-10,
                                           TGF-[beta] in T CD[3.sup.+]
Wang et al. (35)            CD[4.sup.+]    Reduced CD18 expression
                            CD2[5.sup.+]   on Treg cells, which leads to
                            CD12[7.sup.-]  weak function and
                            Treg (mice)    proliferation
                                           Predominant STAT3 pathway
                                           in psoriatic Treg cells leads
                                           to overproduction of IL-6,
Yang et al. (36)            Treg           IL-21, IL-23, resulting in T
                                           effectors activation/Treg
                                           cells isolated from psoriatic
                                           patients could produce
                                           IFN-y, TNF-[alpha], and
                                           IL-17
Th17 and Treg cells
Lochner et al. (38)         FOXP[3.sup.+]  Th17 development is linked
                            Treg           with FOXP[3.sup.+]Treg
                                           depending on TGF-[beta] and
                                           in psoriasis, the impaired
Zhou et al. (39)                           function of Treg cells cause
                                           the hyperactivation of Th1
                                           and Th17
Zhang et al. (21)           FOXP[3.sup.+]  Correlation of Th17
                            Treg           Treg ratio in skin lesions
                                           with PASI was inverse, but
                                           in blood it was positive
Bovenshen et al. (28)       FOXP[3.sup.+]  Treg cells from psoriatic
                            Treg           lesions can differentiate
                                           into IL-17A-positive Th17,
                                           which express IL-17[A.sup.+],
                                           FOXP[3.sup.+], and
                                           CD[4.sup.+] and produce
                                           IL-17A and IL-22 Increase of
                                           the expression of RORyt and
                                           FOXP3, which may suggest that
                                           Treg cells enhance the
                                           inflammatory process, rather
                                           than suppress it
Treg cells and therapy
of psoriasis
Richetta et al. (17)        anti-TNF       Increased Treg cells in
                            therapy        blood of psoriatic patients
Keijsers et al. (24)
Quaglino et al. (43)
Quaglino et al. (43)        etanercept     Normalization of Treg
                                           cell activity
Kagen et al. (10)           alefacept      Stimulating apoptosis of T
                                           effectors, which is enhanced
                                           by Treg cells and causes
                                           remission
Furuhashi et al. (18)       PUVA therapy   Increased Treg cells in
                                           blood after successful
                                           treatment (PASI 90)
Kubo et al. (44)            bath-PUVA      Increases Treg cells
                            therapy        and restores function to
                                           almost normal
Kagen et al. (10)           methotrexate,  Variations of Treg cells
                                           amounts during different
                                           therapies may explain why
                            cyclosporine,  methotrexate and cyclosporine
                            alefacept,     resulted in very short
                                           remissions, but alefacept
                            UVB            and UVB resulted in
                                           long-term ones
Mattozzi et al. (41)        vitamin D      Level correlates with
                                           Treg cells and PASI
                                           Low titer encourages
                                           the activity of Th1,
                                           Th17, and Th22
Ma et al. (45)              anti-TNF       In psoriasis-like disease
                            therapy        provoked by TNF-inhibitors:
                                           TNF-[alpha] neutralization
                                           does not cause the production
                                           of IL-1[beta], IL-6, IL-17,
                                           IL-21, and IL-22, but it
                                           suppresses FOXP3 expression
                                           in the skin with reduction of
                                           FOXP[3.sup.+]Treg

PASI = psoriasis area severity index, TNF = tumor necrosis factor, IL =
interleukin, PUVA = psoralen and UVA.
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Title Annotation:Acta Dermatovenerol APA
Author:Owczarczyk-Saczonek, Agnieszka; Czerwinska, Joanna; Placek, Waldemar
Publication:Acta Dermatovenerologica Alpina, Pannonica et Adriatica
Article Type:Report
Date:Jan 1, 2018
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